The overall theme of this proposal is to identify the conceptus proteins and maternal tissues which interact during early pregnancy and determine, at the molecular level, the effects of these interactions. The rationale for these studies is based on the premise that conceptus proteins mediate some fetal-maternal interactions which are critical to the maintenance of pregnancy and the survival and development of the fetus. We intend to purify, by ion exchange and gel filtration chromatography, the two major polypeptides released into the incubation medium by cultured Day 16 sheep conceptuses. One of these products, ovine trophoblast protein 1 (oTP-1), is the earliest detectable secretory protein and it accumulates in the maternal uterine endometrium where it alters secretion. We plan to identify, by immunocytochemical methodology and competitive binding studies, the areas (caruncular or intercaruncular) and cells of the uterine endometrium with which oTP-1 interacts. The effects of oTP-1 on protein synthesis and prostaglandin metabolism by the endometrium will be determined qualitatively and quantitatively by in vitro studies. oTP-1 will be infused into the uterine lumen of cyclic ewes and the effects of the protein on cycle length, luteal progesterone production and uterine prostaglandin release will be determined. Finally, oTP-1 will be tested for mitogenic activity. Antiserum will be produced in rabbits against the second major blastocyst protein, a high molecular weight glycoprotein (HMWGP). Immunocytochemical methodology will be employed to identify the blastocyst cells which produce the HMWGP and extracellular sites of its deposition. The HMWGP will be tested for immunoprotective activity in vivo and immunosuppressive activity in vitro. Lastly, the major non-serum protein present in uterine flushings from early pregnant ewes will be isolated by a combination of ion exchange and gel filtration chromatography. We plan to immunize rabbits against purified preparations of this protein, attempt to identify the presence of it in conceptus and maternal tissues by immunocytochemical techniques and attempt to demonstrate the synthesis of this protein in vitro by co-cultures of conceptus and endometrial tissues.